Acid-cured coating composition with low free formaldehyde emission and preparation method thereof

Abstract

The present disclosure refers to an acid-cured coating composition with low free formaldehyde emission and preparation method thereof. The acid-cured coating composition comprises an alkyd resin, an amino resin, and an acetoacetyl-functional silicon-based resin, wherein upon curing, the amino resin itself releases at least 0.8 wt % of formaldehyde, based on the weight of the amino resin; weight ratio of the alkyd resin and the amino resin is in a range of from 70:30 to 45:55. The present disclosure also refers to a coated article.

What is claimed is: 
     
         1 . An acid cure coating composition, comprising an alkyd resin, an amino resin, and an acetoacetyl-functional silicon-based resin,
 wherein upon curing, the amino resin itself releases at least 0.8 wt % of formaldehyde, based on the weight of the amino resin;   weight ratio of the alkyd resin and the amino resin is in a range of from 70:30 to 45:55.   
     
     
         2 . The acid cure coating composition according to  claim 1 , wherein the weight ratio of the alkyd resin to the amino resin is in the range from 65:35 to 50:50. 
     
     
         3 . The acid cure coating composition according to  claim 1 , wherein the amino resin is the product of reacting aldehydes with amino compound(s) selected from the group of melamine, urea, benzoguanamine, acetoguanamine and any combination thereof. 
     
     
         4 . The acid cure coating composition according to  claim 1 , wherein the amino resin is butylated amino resin, isobutylated amino resin, methylated amino resin or any combination thereof. 
     
     
         5 . The acid cure coating composition according to  claim 1 , wherein the amino resin has a hydroxyl value of from 50 to 250 mg KOH/g. 
     
     
         6 . The acid cure coating composition according to  claim 1 , wherein acid cure coating composition further comprises a acidic cure catalyst selected from the group consisting of paratoluene sulfonic acid, benzene sulfonic acid, methane sulfonic acid, dinonylnaphthalene sulfonic acid, dinonylnaphthalene disulfonic acid, dodecylbenzene sulfonic acid, oxalic acid, maleic acid, phthalic acid, acrylic acid, ethyl phosphate, phosphoric acid, dimethyl acid pyrophosphate and any combination thereof. 
     
     
         7 . The acid cure coating composition according to  claim 1 , wherein the acetoacetyl functional silicon-based resin is presence in an amount of from 0.1 to 25 wt % relative to the total weight of the acid cure coating composition. 
     
     
         8 . The acid cure coating composition according to  claim 1 , wherein the acetoacetyl functional silicon-based resin is presence in an amount of from 0.7 to 15 wt % relative to the total weight of the acid cure coating composition. 
     
     
         9 . The acid cure coating composition according to  claim 1 , wherein the acetoacetyl functional silicon-based resin comprises acetoacetyl functional groups in an amount of at least 25 wt %, relative to the total weight of the acetoacetyl functional silicon-based resin. 
     
     
         10 . The acid cure coating composition according to  claim 1 , wherein the acetoacetyl functional silicon-based resin has a number average molecular weight of from 700 g/mol to 20,000 g/mol. 
     
     
         11 . The acid cure coating composition according to  claim 1 , wherein the acetoacetyl functional silicon-based resin comprises at least 3.5 wt % of silicon atom, relative to the total weight of the acetoacetyl functional silicon-based resin. 
     
     
         12 . The acid cure coating composition according to  claim 1 , wherein the coating obtained from the acid cure coating composition releases less than 8 μg/inch 2  formaldehyde when tested with a thickness of 100 μm at 25° C. and 50% humidity. 
     
     
         13 . The acid cure coating composition according to  claim 1 , wherein the coating obtained from the acid cure coating composition has a pencil hardness of at least HB. 
     
     
         14 . A process for the preparation of the acid cure coating composition according to  claim 1 , comprising the step of
 mixing an acetoacetyl functional silicon-based resin with an alkyd resin and an amino resin,   wherein upon curing, the amino resin itself releases at least 0.8 wt % of formaldehyde, based on the weight of the amino resin;   weight ratio of the alkyd resin and the amino resin is in a range of from 70:30 to 45:55.   
     
     
         15 . The process according to  claim 14 , wherein the acetoacetyl functional silicon-based resin is in an amount of from 0.1 to 25 wt %, relative to the total weight of the acetoacetyl functional silicon-based resin, the alkyd resin and the amino resin. 
     
     
         16 . A coated article comprising a substrate having thereon a coating formed from the acid cure coating composition according to  claim 1 . 
     
     
         17 . The coating article according to  claim 16 , wherein the substrate is selected from the group consisting of wood, paper, textile, leather, nonwoven, plastics surfaces, glass, ceramic, mineral building materials, metals and coated metals. 
     
     
         18 . The coating article according to  claim 16 , wherein the coating releases less than 8 μg/inch 2  formaldehyde in dried film when tested with a thickness of 100 μm at 25° C. and 50% humidity. 
     
     
         19 . The coating article according to  claim 17 , wherein the coating releases less than 8 μg/inch 2  formaldehyde in dried film when tested with a thickness of 100 μm at 25° C. and 50% humidity.